Loans and Leases - Additional Information (Detail) - USD ($)	3 Months Ended		12 Months Ended
	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Accruing Troubled Debt Restructured Loans and Lease Modifications	$ 542,000		$ 542,000	$ 11,435,000
Loans and Leases Receivable, Net of Deferred Income, Acquired	377,376,000		377,376,000	538,780,000
Carrying amount	695,000		695,000	1,583,000
Value of buyout for buyout leases	1.00		1.00
Impaired Financing Receivable, Recorded Investment	26,581,000		$ 26,581,000
Measure taken to reduce the risk of difference in actual value and residual value of the leased assets at maturity			The Corporation greatly reduces this risk primarily by using $1.00 buyout leases, in which the entire cost of the leased equipment is included in the contractual payments, leaving no residual payment at the end of the lease term.
Charge-offs			$ 15,651,000	7,137,000	$ 6,988,000
Nonaccrual Loans and Leases	26,208,000		26,208,000	14,517,000
Provision for loan losses			20,299,000	9,892,000	4,646,000
Impaired Financing Receivable, Related Allowance	1,415,000		$ 1,415,000	131,000
Maximum modification period on short-term basis			1 year
Restructured loan past due period			90 days
Loans and leases held for investment	4,006,574,000		$ 4,006,574,000	3,620,067,000
Recoveries			3,150,000	1,301,000	2,038,000
Minimum [Member]
Financing Receivable, Recorded Investment [Line Items]
Amount of Loan Relationship Balance, Loans Reviewed Annually	1,000,000		1,000,000
Amount of Loan Relationship Balance, Reviewed Quarterly	15,000,000		15,000,000
Maximum [Member]
Financing Receivable, Recorded Investment [Line Items]
Amount of Loan Relationship Balance, Loans Reviewed on a Performance Basis	1,000,000		1,000,000
Fox Chase Bank [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income, Acquired	314,800,000		314,800,000
Carrying amount	63,000		63,000
Valley Green Bank [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Net of Deferred Income, Acquired	62,600,000		62,600,000
Carrying amount	632,000		632,000
Real Estate-Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Accruing Troubled Debt Restructured Loans and Lease Modifications	0		0	10,266,000
Loans and Leases Receivable, Net of Deferred Income, Acquired	233,625,000		233,625,000	306,460,000
Impaired Financing Receivable, Recorded Investment	18,215,000		18,215,000	16,554,000
Nonaccrual Loans and Leases	18,214,000		18,214,000	4,285,000
Impaired Financing Receivable, Related Allowance	675,000		675,000	99,000
Loans and leases held for investment	1,741,204,000		1,741,204,000	1,542,141,000
Commercial, Financial and Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Accruing Troubled Debt Restructured Loans and Lease Modifications	382,000		382,000	921,000
Loans and Leases Receivable, Net of Deferred Income, Acquired	24,519,000		24,519,000	63,111,000
Impaired Financing Receivable, Recorded Investment	3,747,000		3,747,000	7,079,000
Charge-offs			14,655,000	1,030,000	4,827,000
Nonaccrual Loans and Leases	3,365,000		3,365,000	4,448,000
Provision for loan losses			13,756,000	(66,000)	3,992,000
Impaired Financing Receivable, Related Allowance	413,000		413,000	31,000
Loans and leases held for investment	937,685,000		937,685,000	896,211,000
Recoveries			2,140,000	801,000	1,454,000
Lease Financings [Member]
Financing Receivable, Recorded Investment [Line Items]
Accruing Troubled Debt Restructured Loans and Lease Modifications	0		0	0
Loans and Leases Receivable, Net of Deferred Income, Acquired	0		0	0
Impaired Financing Receivable, Recorded Investment	0		0	1,300,000
Charge-offs			572,000	3,992,000	759,000
Nonaccrual Loans and Leases	170,000		170,000	1,599,000
Provision for loan losses			497,000	4,130,000	314,000
Impaired Financing Receivable, Related Allowance	0		0	0
Loans and leases held for investment	141,956,000		141,956,000	129,768,000
Recoveries			231,000	$ 206,000	$ 191,000
Non-Accrual [Member] | Real Estate-Commercial [Member]
Financing Receivable, Recorded Investment [Line Items]
Nonaccrual Loans and Leases	11,500,000		11,500,000
Impaired Financing Receivable, Related Allowance	624,000		624,000
Loan Participations [Member] | Commercial, Financial and Agricultural [Member]
Financing Receivable, Recorded Investment [Line Items]
Charge-offs		$ 12,700,000
Loans and leases held for investment	13,000,000		13,000,000
Loans and Leases Receivable, Net of Deferred Income, Total Participating Interest From All Parties	80,000,000		80,000,000
Recoveries	$ 1,800,000
Allowance for Loan and Lease Losses Write-offs, Net			$ 10,900,000